Abnormal blood viscosity of small for dates infants and infants from mothers with amnionitis

The viscosity of cord blood from 47 normal infants, 23 small for dates (SFD) infants and 14 infants from mothers with amnionitis was measured at low shear rates to elucidate the fluidity of blood at low flow states. The blood viscosity of the SFD infants was 29.1 ± 12.2 cp (mean ± S.D.) at 0.5 sec^-1 and 13.6 ± 3.8 cp at 3.4 sec^-1, being significantly higher than that of the normal infants ( 18.6 ± 6.5 cp at 0.5 sec^-1; 10.3 ± 2.8 cp at 3.4 sec^-1) (p < 0.01). The levels of viscosity of the infants with maternal amnionitis were 30.2 ± 9.6 cp at 0.5 sec^-1 and 14.1 ± 3.5 cp at 3.4 sec^-1, being also significantly higher than the normal ones (p < 0.01). The measurements of hematocrit and fibrinogen levels of the infants of the three groups revealed that the increased blood viscosity in the SFD infants was due to increased hematocrit and in the infants with maternal amnionitis due to increased fibrinogen. It was suggested that in such abnormal fetuses, increased clumping and sludging of red blood cells would occur in fetal and feto-placental microcirculation and impair the tissue oxygenation of the fetuses during parturition.